Re: [PATCH v5 3/9] mm: Add write-protect and clean utilities for address space ranges

["Thomas Hellström (VMware)" <thellstrom@vmwopensource.org>]

On 6/12/19 1:23 PM, Christoph Hellwig wrote:
> On Wed, Jun 12, 2019 at 08:42:37AM +0200, Thomas Hellström (VMware) wrote:
>> From: Thomas Hellstrom <thellstrom@vmware.com>
>>
>> Add two utilities to a) write-protect and b) clean all ptes pointing into
>> a range of an address space.
>> The utilities are intended to aid in tracking dirty pages (either
>> driver-allocated system memory or pci device memory).
>> The write-protect utility should be used in conjunction with
>> page_mkwrite() and pfn_mkwrite() to trigger write page-faults on page
>> accesses. Typically one would want to use this on sparse accesses into
>> large memory regions. The clean utility should be used to utilize
>> hardware dirtying functionality and avoid the overhead of page-faults,
>> typically on large accesses into small memory regions.
> Please use EXPORT_SYMBOL_GPL, just like for apply_to_page_range and
> friends.

Sounds reasonable if this uses already EXPORT_SYMBOL_GPL'd 
functionality. I'll respin.

>    Also in general new core functionality like this should go
> along with the actual user, we don't need to repeat the hmm disaster.

I see in your later message that you noticed the other patches. There's 
also user-space functionality in mesa that excercises this.

/Thomas